302 CARNEGIE INSTITUTION OF WASHINGTON. 



water, drain, and air pipe-lines, and lead-incased electric cables from 

 the main laboratory are hung underground in a concrete tunnel suffi- 

 ciently large to allow alterations and additions in accordance with the 

 future development of the experimental work. Provision is made for 

 14 complete direct-current circuits between the two buildings, and for 

 3 alternating-current circuits. The outside dimensions of the Experi- 

 ment Building are 28 by 53 feet; the inside dimensions are 25 by 50 

 feet with a clear height below the exposed roof-trusses of 12 feet. The 

 inside of the building is plastered in hard sand finish, while the outside 

 is finished in stucco with exposed aggregate of coarse crushed granite 

 and mica. The sill courses about the building and under windows 

 and the columns at the entrance, all cast in place, are of artificial stone 

 with fine granite-and-mica surfacing. 



The Experiment Building was completed and ready for use by the 

 Division of Experimental Work early in October. Much time was 

 required for the construction because of the scarcity of materials and 

 of labor under prevailing conditions. 



The Division has also had general charge of the maintenance and 

 care of the main laboratory. Standardizing Magnetic Observatory, 

 foundry, and auxiliary buildings. The necessary extension to the 

 switch-board in the main laboratory to provide for the new circuits to 

 the Experiment Building was mounted in the motor-generator room. 



A waiting-room, 8 by 12 feet, was constructed during November and 

 December 1918 at the west corner of Thirty-sixth Street and Con- 

 necticut Avenue, to provide shelter for the members of the staff in bad 

 weather. 



Tile drains for road drainage were installed and the necessary filling 

 and rough grading for a new roadway between the main laboratory 

 and foundry and stable were completed. The macadamized roadways 

 in the grounds were repaired, having been badly damaged during the 

 heavy hauling incidental to the construction of the Experiment Building. 



ABSTRACTS OF PUBLICATIONS AND INVESTIGATIONS. 



On determination of position of airplanes by astronomical methods. J. P. Ault. (Pre- 

 sented before the American Physical Society at Washington, April 25, 1919.) 



The problem confronting the navigator, either at sea or in the air, is to 

 measure as accurately as possible the altitude of some celestial body such as 

 the Sun, Moon, or stars. From this measured altitude a line of position, a so- 

 called Sumner line, is determined, the observer being located somewhere on 

 this line. If two celestial bodies are available, then the intersection of the two 

 lines thus determined completely fixes the geographic position of the observer. 

 If one object only is available, as for example the Sun, then in order to com- 

 pletely determine a position it is necessary to observe in addition the azimuth 

 or bearing of the body. The altitude, usually measured with some form of 

 sextant, is the angular distance of the body above the horizon. For ocean 

 navigation, the sea-horizon is generally available, but for airplane work some 

 artificial horizon must be provided. 



